Strong influence of polaron-polaron interaction on the magnetoresistance effect in La_(0.7)A_(0.3)MnO_3 thin films

摘要

The colossal magnetoresistance effect endows La_(0.7)A_(0.3)MnO_3 manganites distinctive fascination. Both theoretical and experimental studies demonstrated that the interplay among polarons could significantly influence magnetoresistance. However, the underlying microscopic mechanism of the influence remains elusive due to the lack of experimental evidences. Utilizing ultrafast optical spectroscopy to track the polaron dynamics around Curie temperatures, we observed a diverse two-step recovery process in three sibling manganite thin films with various magnetoresistance effects and Curie temperatures, while the slow step was proposed to be the formation evolution of correlated polarons through the polaron-polaron interaction. Polarons in La_(0.7)Ca_(0.3)MnO_3 equilibrate much faster than those in La_(0.7)(Ca_(0.58)Sr_(0.42))_(0.3)MnO_3 and La_(0.7)Sr_(0.3)MnO_3, indicating a comparatively tighter interaction between polarons and subsequently a stronger magnetoresistance effect.